[PATCH] D87335: [json] Create some llvm::Expected-based accessors

[Sam McCall via Phabricator via llvm-commits]

sammccall added a comment.

This is a sensible thing to want and very nice code.
I'm not sure about putting it in JSON.h - there are a few unfortunate aspects that I just don't know how to fix, but limit the benefit which has to be measured against the cost of adding more complexity to the API.

- the error messages aren't *quite* good enough to be directly user-visible in the general case. e.g. "JSON object missing the 'id' field" - some hint to which (sub)object is often needed. U
- because the getAsX() method names are taken, the new accessors are stuck with awkward names
- Expected<pointer> (for object/array) is an awkward type, because -> doesn't really work and the meaning/impossibility of nullptr isn't obvious.
- this is useful when mapping objects with many fields, but it's not clear how to extend it to ObjectMapper or fromJSON (which maybe themselves don't have the best design, but...)




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  https://reviews.llvm.org/D87335/new/

https://reviews.llvm.org/D87335